This invention relates to cannulae for extracorporeal perfusion of fluid, and more particularly to peripheral cannulation procedures.
Numerous medical procedures involving the transfer of blood to or from a patient require cannulae to provide the fluid path. Such procedures include total and partial bypass of the heart and lungs, with the bypass route being a cannula appropriately seated within the circulatory system. In addition to bypass of a given section of the circulatory system (for example, the heart during open-heart surgery), extracorporeal transfer of the blood may have additional objectives such as artificial oxygenation of the blood as with a lung bypass procedure.
Conventional cannulae are effective in transporting fluid from an external source to the vein or artery affected; however, they are not designed to provide adequate dispersion by establishing flow gradients to maintain proper circulation through various tributaries of the subject vein or artery. They typically transport the blood to the artery or vein and allow natural fluid flow to seek the appropriate paths of distribution through the circulatory system. This procedure results in abnormal fluid pressures and inappropriate flow gradients at the point of extracorporeal entry as well as at branching locations of the subject vessel.
Furthermore, such cannulae typically possess thick wall structure, increasing the size of incision required to insert the cannula within the vessel. Where the cannulation procedure utilized required bidirectional flow to maintain blood in the extremities while infusing the major portion of blood toward the larger channels of circulation even larger or double incisions are required. Such larger incisions result from prior art techniques which require the use of separate cannulae inserted through a large single incision or two separate small incisions along the opposing bidirectional vessel paths, each cannula supplying fluid in accordance with the need of the particular portion of the circulatory system affected. Not only does this two cannula technique result in adverse flow characteristics at the respective points of entry, but the larger incision creates surgical difficulties such as increased risks of infection, seepage of blood, difficulty in post-operative repair and inordinate damage to tissue and vessels.